Now, just for kicks, did you know you can start up multiple instances of
X, on the same box (say, one for you, one for the wife, one for the kid,
etc)?

That's about the same as the so much advertised "Switch User" feature in windoze XP. The big difference is that Linux/X can do this for ages ;)

If I'm not mistaken, "Switch User" only works in XP Home, not in XP Pro.
Since 99% of my dealings are with Pro in the workplace, I'm constantly
frustrated by this limitation (as well as others) in XP Pro. I think
I've only tried it once on XP Home, and my vague memory is that I found
this feature to be woefully lacking. But perhaps my memory is colored by
my biases.